Tag: GM-70

Teflon Sockets

I’ve got a set of teflon sockets from Jakeband. These are fantastically made to order. Luciano from Jakeband sent me in addition some samples which I will use in the eTracer which I will bring along to ETF.19.

Jakeband socket examples

Honestly, these are fine pieces of craftwork. For example, you can measure and let Luciano know the diameter of your 845 (or any other transmitting valves) when ordering these valves so they fit perfectly.

I’ve used these sockets on my projects for years and am very pleased have to say. Of course you pay a premium price as these are hand-made with fine materials. In my opinion, these are worth every cent.

Also I had a pair of RCA sockets, look at them:

RCA female connector

They are made on a single piece of tellurium copper. First coating in pure silver 99.99% thickness 18 microns and the second coating Gold 24 K 3 micron thick. Sterling job!

You can contact Jakeband directly to order your sockets. Just use the form I posted years ago here.

GM-70 SE Amplifier

I keep getting requests about SE amp designs using the 6SF5 driver. Here is what I have come up with for the 6SF5 driving the GM-70. With only one stage you can drive the GM-70 to full power and get 18W out of this lovely transmitting valve: Continue reading “GM-70 SE Amplifier”

813 triode SE with 4P1L Pentode

A monster DHT amp

Lately I haven’t had any time for audio work unfortunately. Changing nappies to a 4 week old baby whilst working long hours is tough. I can get the odd 30 minute here and there and every time I try to get upstairs to the workshop something pops up. Never mind, hopefully things will get easier in the near future.

I’ve been asked about the 4P1L pentode driver. It’s been a long time since I did those tests and never got around to listen to the driver sound. Tests were promising but never managed to include this driver on my amp.

Driving transmitting valves is a challenging task. Especially if we want to take them to A2-land (unless they operate in A2 whilst in zero grid bias). Driving big transmitting valves like 211, 805, 845, 813 or GM-70 require a large swing of volts for the driver which should do this linearly. The load is quite demanding in particular when we approach the grid to 0V (or biased positively) and using a triode as driver also puts a daunting task to the previous stage due to the Miller effect. It’s not easy to find triodes that can swing 300Vpp with very low distortion.

Continue reading “813 triode SE with 4P1L Pentode”